Process of casting iron in permanent molds at a regulated cooling rate



Patented Aug. 31, 1926.

UNITED STATES PATENT omcs.

DANIEL H. MELOCHE, 015 DETROIT, MICHIGAN, ASSIGNOR TO EARL HOLLEY, OF

DETROIT, MICHIGAN.

PROCESS OF CASTING IRON IN PERMANENT MOLDS AT A REGULATED COOLING RATE.

No Drawing. Continuation of application Serial No. 609,145, filedDecember 26, 1922. This application filed March 3, 1923.

The object of this invention is to define a procedure which if followedwill enable any foundryman to produce from a permanent mold every one,two or three minutes a machineable casting superior to those produced inordinary sand molds.

Thisapplication is a continuation of my application, Serial No. 609,145,filed by me on the 26 of December, 1922.

In order to produce homogeneous castmgs (i. e. castings of uniformhardness or softness) in permanent molds I have found it necessary toprotect the surface of the mold with a refractory, inert andheat-insulat ng paint which is very adhesive and hav ng protected itcover it between each casting with a thick renewable coating oflampblack, 7

whereby a fresh coating of lampblack is presented to the metal each timethe metal 1 is poured into the mold.

The molds themselves are made of cast iron having substantially the samecomposition as the iron cast therein, for the reasons set forth in myco-pending application Serial No. 576,632, filed 21 July, 1922.

This application describes the use of a cast iron mold in which the castiron has very little combined carbon. In other words, the mold is madeof soft gray iron.

Briefly my process consists in regulating the following factors, which Ifind determine the success of the process 1. The temperature of the ironpoured.

2. The temperature of the molding surface of the permanent mold.

3. The thickness of the walls of the permanent molds when made of castiron.

1. The provision of an insulating refractory adhesive inert lining forthe purpose of retaining the heat within the metal cast as set forth inmy Patent #1,453,593, fied Angust 11th, 1922, issued May 1st, 1923.

5. The application of a thick pulverulent coating of lampblack as setforth in my co pending application, Serial No. 579,927, filed 5 August1922.

6. The thorough cleaning of the walls of the molds before applying thelampblack, as set forth in the co-pending application of J. L. Dostal,Serial No. 568,405, filed 15 June 1922.

7 Yielding means for holding the molds Serial No. 622,675. 1

together, whereb the enormous pressure developed when 11.0I1 freezes ina confined space is avoided, as disclosed in United States patent toMcWane, #1,083,122, dated December 30, 1913..

8. The prevention of leaks by providing a narrow bead or rim around themolds so that the molds contact on a relatively narrow edge as disclosedin the United States patent to Phillips, #1,099,997, dated June 16,1914.

9. When large castings are produced continuously cooling means may bearranged as shown in the co-pending application of De ForestWzCandlenSerial No. 558,396, filed 4 May 1922.

10. The composition of the iron' cast.

11. The composition of the metal molds. In order to make the continuouscasting of gray iron castings in permanent molds a commercial success itis obviously necessary to eject them at the earliest practical moment.That is to say at a temperature of about 1650 F which is 200 F. abovethe critical temperature. By so doing the rate of cooling is checked atthis temperature and the problem of providing cooling means for thepermanent molds is greatly simplified, except with large castings, andthus a greater production per mold may be obtained.

In order to get clear definition the iron must be poured at a goodyellow heat. That is to say it should be poured at a temperature inexcess of 2200 F. These conditions are quite severe and great difficultyhas been exchilling of the iron in the molds as, if this is not done,the castings produced will be unmachineable. is to solidify the outersurface and leave the core liquid. It is afact well known in the artthat the cooling of the molten interior The efi'ect of a sudden ehill'will not provide sufficient heat to soften the v skin by annealing, asit has been found that once the hard spots have been formed on thesurface of the casting due to chilling, that these hard spots areextremely difficult to correct even when heated for a long time so as togive a prolonged annealing.

The process I have invented consists as follows I The molds may beproduced in any suit able manner, e. g. from a dry sand mold and a drysand core. The mold surface or the dry sand mold and core may beprotected by an adequate coating of lampblack and is preferably dustedwith a lycopodlum powder. A rib or bead may be cast around the ironmolds so as to faciiitate the machining of the surface as matchedtogether, as set forth in the United States patent to Phillips citedabove. These molds may well be cleaned with a small hand grinder toremove the outer skin'. Obviously the molds themselves may be cast in apermanent mold.

The molds may then be heated for about. one hour to about 1500 F. torelieve the strains which would otherwise result In distortion. Themolds are then painted at a temperature of about 500 The paint which Iprefer to use COIISISFS. of a 10% saturated solution of sodium slhcate mwater mixed with an equal weight of finely ground fire clay. Thequantity of fire clay,

however, may be reduced somewhat where the mold having the coatingapplied thereto is designed for the casting of compl cated castings whena somewhat thinner paint is desirable, as set forth in my co-pendingapplication, Serial No. 581,239 filed 11 August 1922.

When it is necessary to apply a thick coating the cast iron mold israised to a temperature above 1000 F after each layer of approximately.01 is apphednn order to bake on each layer as it is applied. By sodoing I have succeeded in building up a coating having a thickness ofA". After the desired thickness is attained a final application of heatis applied in order to make the lining of fire clay permanent. a

Over the coating of refractory fire clay referred to above a relativelythick layer of lampblack is applied. In order to determine that theright thickness of lampblack has been applied, the test is to notewhether after the casting has been ejected and before the mold has beencleaned with a blast of air, it is substantially intact.

In the commercial production of two pound castingshaving sectionsvarying from 1 g 't0'{1 inthickness I have obtained excellent results-by 1 using hollow cast iron' molds having a wall protected with arefractory lining with a superimposed coating of lampblack renewedbetween. each casting. When runningthemolds so. its to pour iron inthemolds every 1% or 2 minutes, the surface of the molds attain atemperature of approximately 1000 F., the castings ejected having abright red color. lVhen larger castings are produced conditions must beadjusted so that the period taken to solidify does not greatly exceed 30seconds and with smaller castings the conditions must be modified sothat the period taken is not much less than this 30 seconds.

The rate of pouring, or rather the periods between successive operationsof each mold, is regulated by the heating effect of the molten iron uponthe mold, hence with larger castings a longer period of time should beallowed in order to keep the temperature of the face of the mold below1150 E, which is the highest temperature at which it is commerciallypossible to carry on this process. Above 1150 F. the lampblack will notadhere and hence the process cannot be practiced as described in this application. \Vith large castings I may also make use of the air coolingmeans described in the application of De Forest IV. Candler, Serial N 0.558,396, filed 4 May 1922, in order to hold. the temperature of themolds within the desired limits.

The molds are mounted upon a horizonthey are heated to a temperature inexcess 1 of 212 F. as a precaution against the possibility of any waterbeing left on the surface which would cause a blowback. The first fewcastings are rejected as scrap, the purpose of pouring these castingsbeing merely to raise the temperature of the molds to the. lowesttemperature at which soft castings can be secured which is about 650 F.The molds are opened slightly a few sec onds before the molds are openedwide fo the ejection of the casting. thus relieving all pressure betweenthe molds at the earliest possible moment which is after about 15seconds.

After the casting is ejected by mechanism substantially equivalent tothat disclosed in the eo-pending application of De Forest W.

Candler, Serial No. 504,988, filed'3 Octoher, 1921, a blast of air isdirected ontofthe working surface of the mold, etc., for the purpose ofremoving any loose dirt, as disclosed in the co-pending application ofJ. L. Dostal, Serial No. 568,405, filed June Thelampblack is thenreapplied after each casting operation by means of a burner which iscarried with the moldsand automatically released and carried by the nextsucceeding mold, as shown in the co-pending application of J L. Dostal,Serial No. 590,- 913, filed the 27th of Sept, 1922. Thetype of burnerused is that shown in this application, which is the subject matter of adivisional application, Serial No. 619,557, filed 17 February, 1923.

The iron cast in the iron molds may preferably be somewhat higher insilicon than many commercial cast irons, thus corresponding to thehigher grade-of cast iron known commercially as #1 foundryiron. Thisiron has a silicon content greater than 2.75%, a manganese contentbetween 4% and .691. The total carbon content in this iron runs from2.50% to 3.50% and the combined carbon of the pig is less than 0.7%.Sulphur, oxygen and phosphorus are held at a low figure as they areobjectionable for the same reasons as in sand castings. However, owing.to the sudden cooling of the iron there is less time for segregation inthe mold and hence the danger: of the formation of manganese sulphide inthe iron whilst it is solidifying in the molds is lessened as comparedwith sand castings. The composi-' tion of the iron cast and the castiron molds are preferably the same, as set forth in my co-pendingapplication, Serial No. 576,632, filed 21 July, 1922.

In melting this #1 foundry iron it is preferable not to add more thanlow carbon steel scrap to carbon),

. and very satisfactory results can be obtained without any steel scrapat all. The cupola blast is regulated so that the melting zone isconfined to a few inches and thus the iron does not have any appreciableoxygen (iron oxide). The percentage of combined car.- bon is alsoreduced by avoiding the chilling effect of a strong blast of cold air,it being always remembered that it is much easier to form combinedcarbon than it is to anneal so as to release the combined carbon. Thatis to say, to correct the trouble once it has been created. A mixture ofscrap and 50% pig is satisfactory providing the scrap has a similarcomposition to that given above.

lBy retaining the heat of the molten iron Y inthe molten iron longenough to permit the silicon to precipitate all the carbon and notretaining the heat long enough to permit the large crystalline growth socharacteristic of ordinary sand cast, I produce an improved productdescribed in my co-pending application Serial No. 618,715, filed 12February 1923, which is a continuation of my co-pending application,Serial No. 559,-

By the use of a gray cast iron mold having little or no combined carbonI obtain an adherent coating of fire clay. The fact that the gray ironhas a more open grain structure than either steel or white iron probablyenables the coating to be so' adherent.

hat I claim is:

1. The process of producing self-annealed gray iron castings in metalmolds, which consists in first coating themolding surfaces with anadherent inert insulating refractory lining in order to provide apermanent lining, then superimposing a renewable coating of'amorphouscarbon, then pouring the iron into the mold, the said layer of amorphouscarbon being sufficiently thick so that it will be substantially intactafter the casting is ejected.

2. The continuous process of producing self-annealed gray iron castingsin metal molds which consists in heating the molds then painting thesurface of the mold with a wash in which a heat-resisting adhesive isdissolved and an inert refractory substance 15 suspended in order toprovide a permanent lining, then coating the mold with a relativelythick renewable coating of amorphous carbon, holding the molds closed bya yielding pressure, pouring iron into the molds, ejecting the castingsabove the critical temperature and maintaining at all times. an excessof lampblack so that at all times after the ejection of the casting'thecoating of lampblack remains practically intact.

3. The continuous process of producing self-annealed gray iron castings.which consists in heating the molds to 500 F., then painting the moldsurfaces with a permanent coating of an adherent inert insulatingrefractory substance in order to provide a per manent lining, thenapplying a thick renewable coating of amorphous carbon of such athickness that it is practically intact after the ejection of thecasting, so that at all times the castings are cast in an excess oflampblack, then permitting the temperature still above the criticaltemperature of 4.. The continuous process .of producing self-annealedgray iron castings in permanent molds, which consistsof first heatingthe metal molds to a temperature in excess of 400 F., then painting themetal molds with a refractory inert insulating coating mixed with atemperature-resistingadhesive in order to provide a permanent lining,then applying a thick coating of amorphous carbon and maintaining thecarbon coating at such a thickness that it is' substantially intact atall times, second, melting iron of from 2.50% to 3.50% total carbonandof from 1.75% to 2.75% silicon, pouring the iron into the molds andfinally ejecting the castin s from themolds themoment they have su'ciently solidified. i no 5. The continuous process of producingself-annealed gray iron castings 1n permanent molds having substantiallythe same composition as the iron cast therein, consisting first ofheating the cast iron molds to above 400 F, then painting the molds with4 a refractory inert insulating wash containa ing.

ing'a little soluble silicate in solution and a considerable quantity ofa refractory powder in suspension in order to provide a permanentlining, then coating with a renewable coat of lampblack and maintainingthe lampblack by frequent applications suficiently thick so that it willbe substantially intact after the castings are ejected from the molds,second, melting iron of from 2.50% to 3.50% total carbon and from 1.75%to 2.75% silicon, pouring the iron into the molds and finally ejectingthe castings from the molds at a temperature greater than 1450? F. andpermitting the molds to reach a temperature between 650 F. and 1150 F.

6. The process of producing self-annealed gray iron castings inpermanent molds, which consists in pouring iron at over 2200 F.into-molds protected by a permanent adherent inert refractory insulatinglining and a super-imposed renewable coating of amorphous carbonsufficiently thick so that it will be substantially intact when thecasting is removed, whereby the heat of the metal cast is retainedwithin the casting and the solidification of the casting is delayed.

7. The process of producing,self-annealed 1 gray iron castings inpermanent molds,

which consists in pouring iron substantially free from oxygen at atemperature in excess of 2200 F. into molds protected by a permanentadherent inert refractory insulating lining and a super-imposedrenewable coating of amorphous carbon sufficiently thick so as to besubstantially intact when the casting is removed, whereby the heat ofthe metal castis retained within the cast- 8. The process of producingself-annealed gray iron castings in hollow metal molds, which consistsin first heating the molds to 500 F., then applying a thin permanentlining of an inert refractory insulator made adherent by aheat-resisting binder, then super-imposing a renewable coating ofamorphous carbon sufficiently thick so that it'will be substantiallyintact when the casting is removed, then pouring iron into the mold atover 2200 F., holding the casting within the mold and then removing thesurplus lampblack by means of a compressed gas so that only a thincoating of lampblack remains on the mold, renewing the lampblack coatingwith fresh lampback, closing the molds, again pouring the iron andrepeating the cycle sufliciently frequent so that the temperature of themolds is betw n 6 0 F.- a d l R 9. The process of producingself-annealed gray iron castings in iron molds having relatively thinwalls, which consists in protecting the molds by means first of arelatively permanent refractory insulating adherent lining, then coatingthe molds with a pulverulent coating of lampblack, then pouring in ironhaving a temperature in excess of 2200 F., allowing the casting tosolidify, then ejecting the casting, then cleaning the molds of residuallampblack and dirt, then renewing the lampblack coating, closing themolds again, pouring the iron in the molds and repeating the cycle ofoperation until the temperature of the mold attains a temperature ofbetween 650 F. and 1150 F., whereby the castings remain liquid in themolds for from 25 to 35 seconds. I

10. The process .of producing self-annealed grayv iron castings, whichconsists in casting a mold of iron with a wall thickness ofapproximately applying a permanent adherent inert refractory insulatinglining of approximately then superimposing a renewable coating oflampblack approximately thick, pouring in iron at a temperature above2200 F., ejecting the castings at a temperature above 1450 F. andrepeating the cycle of operation sufficiently frequently whereby themolds attain atemperature of above 650? F. and below 1150 F.

11. The process of producing self-annealed gray iron castings inpermanent metal molds which consists in first protecting the moldingsurfaces with an adherent inert. refractory insulating lining which ispermanent, superimposing a coating of amorphous carbon suflicientlythick so that -it will be substantially intact when the casting isremoved, pouring iron into the mold at a temperature above 2200 F.,openin the molds immediately the casting has soli ified, ejecting thecasting whilst its temper ature is still above 1450 F., removing thesurplus carbon with a blast of air and then recoating with lampblack,whereby a fresh coating of amorphous carbon is presented to the ironeach time iron is poured into the mold, repeating the cycle of operationsufliciently frequently so that the temperature of the molding surfacesexceeds 650 F. and is less than 1150 F.

12. The process of producing self-annealed gray iron castings inpermanent metal molds which consists in first protecting the moldingsurfaces with an adherent inert refractory insulating coating which ispermanent, super-imposing a renewable coating of amorphous carbon,pouring iron into the mold at a temperature in excess of 2200 F.,opening the molds and ejecting the castings, removing the surplus carbonand replacing with a fresh opating of lampblack, repeating the cycle ofoperation sufficiently frequently so that the temperature of the moldingsurfaces does not exceed 1150 F. and does exceed 650 F.

13. The method of pouring gray iron into a smoke protected refractorymold, ejecting the casting formed therein, repeating the operation so asto maintain the temperature of the mold surfaces at such a point as willcause the iron cast therein to freeze in 10 from twenty to fortyseconds, Wherebythe carbon is all precipitated as finely dividedgraphite.

In testimony whereof I afiix my signature.

DANIEL MELOCHE.

